Recent advances in wireless and portable electronic devices such as laptops, cellular phones, camcorders, and radios have fueled interest in the area of micro-power sources with enhanced energy and power densities relative to existing battery technologies. Similarly, military applications requiring portable power for long-duration missions, autonomous vehicles, and remote sensors have focused increased attention to this area. Developments in integrated circuit (IC) hardware have also necessitated on-chip power sources capable of delivering actuation, sensing and controls requiring more compact packaging.
Fuel cells have become one of the leading candidates to fill the need of increasingly power-hungry portable electronic devices. Fuel cells have the potential to provide higher energy densities relative to batteries (especially when using liquid fuels). Fuel cells also offer the prospect of instantaneous refueling and high energy conversion efficiency. Fuel cells also have the inherent characteristic of vibration free and low-noise operation, a key requirement for personal power packs.
Solid oxide fuel cells (SOFCs) are high temperature fuel cells, usually operating at 500° C. or higher. At high temperatures, electrode reaction rates are enhanced, and non-noble metal catalysts such as pervoskite/flourite oxides and Ni metal can be utilized. In addition, SOFCs have been demonstrated to be capable of directly using high energy density hydrocarbons such as methane, propane and butane, thus reducing the need for fuel reformers and easing system integration into the current fuel infrastructure. Operation at high temperatures, however, requires the use of thermally resistant and gas-tight separators, manifolds, and seals leading to significant engineering challenges and increased the overall complexity of this system. Accordingly, the fabrication of suitable devices can be challenging.
Recent advances in SOFCs have shown that by using chemically selective catalysts at the electrodes, the fuel cells can operate with both fuel and oxidant introduced into a single compartment. This design, called the single chamber fuel cell (SCFC), has received increased interest due to its simplified cell construction. However, one challenge associated with micro-SCFCs is that high fuel and oxidant flow rates may be required to obtain high power performance. When high flow rates are employed, fuel utilization is poor, lowering the overall efficiency of the SCFC and rendering them less attractive.
Accordingly, improved systems and methods are needed.